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From: Pavel Stehule <[email protected]>
To: Sascha Kuhl <[email protected]>
Cc: Fujii Masao <[email protected]>
Cc: Tomas Vondra <[email protected]>
Cc: Kyotaro Horiguchi <[email protected]>
Cc: Tom Lane <[email protected]>
Cc: Peter Eisentraut <[email protected]>
Cc: PostgreSQL Hackers <[email protected]>
Subject: Re: sequences vs. synchronous replication
Date: Tue, 28 Dec 2021 09:50:39 +0100
Message-ID: <CAFj8pRAs4+T1ADZOzi-5z4R+0Dmz+20vPi8dq5L-Ru8anvQLXQ@mail.gmail.com> (raw)
In-Reply-To: <CAPvVvKDjqozx5szNTRthNiFePBvPT+Td0e8rqjb23oF8Py4e6A@mail.gmail.com>
References: <[email protected]>
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Hi

út 28. 12. 2021 v 9:28 odesílatel Sascha Kuhl <[email protected]>
napsal:

> Sequence validation by step, in total is great. If the sequence is Familie
> or professional, does it make sense to a have a total validation by an
> expert. I can only say true by chi square Networks, but would a medical
> opinion be an improvement?
>

Is it generated by boot or by a human?



> Fujii Masao <[email protected]> schrieb am Di., 28. Dez. 2021,
> 07:56:
>
>>
>>
>> On 2021/12/24 19:40, Tomas Vondra wrote:
>> > Maybe, but what would such workload look like? Based on the tests I
>> did, such workload probably can't generate any WAL. The amount of WAL added
>> by the change is tiny, the regression is caused by having to flush WAL.
>> >
>> > The only plausible workload I can think of is just calling nextval, and
>> the cache pretty much fixes that.
>>
>> Some users don't want to increase cache setting, do they? Because
>>
>> - They may expect that setval() affects all subsequent nextval(). But if
>> cache is set to greater than one, the value set by setval() doesn't affect
>> other backends until they consumed all the cached sequence values.
>> - They may expect that the value returned from nextval() is basically
>> increased monotonically. If cache is set to greater than one, subsequent
>> nextval() can easily return smaller value than one returned by previous
>> nextval().
>> - They may want to avoid "hole" of a sequence as much as possible, e.g.,
>> as far as the server is running normally. If cache is set to greater than
>> one, such "hole" can happen even thought the server doesn't crash yet.
>>
>>
>> > FWIW I plan to explore the idea of looking at sequence page LSN, and
>> flushing up to that position.
>>
>> Sounds great, thanks!
>>
>> Regards,
>>
>> --
>> Fujii Masao
>> Advanced Computing Technology Center
>> Research and Development Headquarters
>> NTT DATA CORPORATION
>>
>>
>>


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